I am newly married and my husband and I take part in intimate activities almost every day and I know that Ghusl e janabat is wajib with washing hair and body. However due to my hair being long and very thick, I find it very difficult to wash it everyday as well as it being tied up under hijab all day and because of this I sometimes get into arguments with my husband to not be intimate as I am not able to wash my hair afterwards and do not want to have to miss prayers. Is there any way of avoiding washing my hair while doing Ghusl e janabat or is there a simplified method of doing Ghusl e janabat?

This is the rulings of Ayatullah Sistani (May Allah protect him)

Ruling 378. In ghusl, short hair that is considered part of the body must be washed. It is not obligatory to wash long hair. In fact, if one makes water reach the skin in a way that the hair does not become wet, the ghusl is valid. However, if it is not possible for water to reach the skin without the hair becoming wet, then one must wash the hair in a way that water reaches the body.

Reference :
https://www.sistani.org/english/book/48/2168/